1. Field of the Invention
This invention is in the general field of methods and apparatus for reducing power dissipated by an electronic system and, more particularly is a method and apparatus for reducing power dissipated by an electronic system by varying a system clock frequency.
2. Description of the Prior Art
In an electronic system that includes semiconductor devices, such as a microprocessor, power dissipation is of critical importance because it causes a temperature rise that may be destructive. In order to tolerate the temperature rise, it is desirable to operate the microprocessor at as low a temperature as possible. The desirability of operating at the low temperature may necessitate the use of a heat sink that is expensive and cumbersome.
The system usually includes a system clock that provides clock pulses which synchronize internal operations of the microprocessor to other elements of the system. One criteria of the usefulness of the microprocessor is the maximum clock frequency at which it will operate. However, an increase in clock frequency results in an increased power dissipation. Hence, the increased power dissipation militates against the operation of the microprocessor at the maximum clock frequency.
A significant amount of power is collectively dissipated by personal computers because their use as a tool of industry and their home use has mushroomed. Because of the mushroomed usage, construction of what is known as a GREEN PC is under consideration for environmental reasons. The underlying concept of the GREEN PC is operation at a reduced power level when the GREEN PC is idle. Heretofore, reduction in the power level of an electronic system when it is idle has been uneconomical and impractical.